Catalyst for catalytic reduction of nitric oxide with ammonia having titanium oxide as the main component exhibits superior activity and durability, and as such, has been widely used for treatment of boiler exhaust gas, and has become mainstream of the catalyst for NOx reduction (see Patent Document 1 and the like).
With the recent increase in demand for energy, a variety of fuels have been increasingly in use such as coal with high sulfur content (high S coal), PRB coal, biomass and the like, and with this trend, the mode of deterioration of NOx reduction catalyst for exhaust gas is also becoming diverse. Some of the well known examples include the deterioration by arsenic (As) compounds as often seen with the use of high S coal, the deterioration by P compounds as often seen with the use of PRB coal, and the deterioration by potassium (K) compounds as often seen with the use of biomass fuel. All of these are known to be caused by the accumulation of catalyst poison that quickly accumulates in the catalyst, inducing a significant decrease in the NOx reducing ability in a short amount of time.
In regard to the above, the inventors of the present application have already invented a Ti—V—Mo—P based catalyst that prevents accumulation of the aforementioned poisons in titanium oxide and have filed an application for a patent (see non-prior art: Patent Document 2).